Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$151.89	9.300%	$166.0158	$166.02	$166.00	$166.00
Purchase #2	$5.36	11.285%	$5.9649	$5.96	$5.95	$6.00
Purchase #3	$9.83	12.507%	$11.0594	$11.06	$11.05	$11.10
Purchase #4	$59.36	3.758%	$61.5907	$61.59	$61.60	$61.60
Purchase #5	$74.30	12.349%	$83.4753	$83.48	$83.50	$83.50
Purchase #6	$116.60	11.625%	$130.1548	$130.15	$130.15	$130.20
Purchase #7	$141.96	8.467%	$153.9798	$153.98	$154.00	$154.00
7 purchase totals =	$559.30		$612.2407	$612.24	$612.25	$612.40